A guitar is typically composed of a neck and a body. The strings are attached to the end of the neck on one end and to the body of the guitar on the other end. Since guitar strings are under continued tension, they place very high forces on the joint between the neck and the body, especially since the neck acts as a long lever.
Some guitar designs attach the neck joint by glue (i.e. the Gibson set neck design), and some attach it by bolts. In either case, to prevent the neck from moving or breaking under the tension of the strings, the neck typically comprises a heel at the joint between the body and the neck. The heel is a protrusion that extends throughout the thickness of the guitar body and provides structural support for the neck joint to ensure stability. Since guitar strings are under continued tension, it is important to connect the neck to the body in a way that will support the tension of the strings and prevent the neck from moving.
Unfortunately, while a heel is very good at providing structural stability to the neck joint, it also takes up space. In particular, the heel can block a guitar player's hand when the player tries to reach very high notes on the instrument, since those high notes are located at the neck joint. The neck is typically 21-24 frets in length; to ensure structural stability, the heel has to start at approximately the 15th fret. That makes the higher frets hard to access.
Also, a traditional square neck joint only bears tension on the bottom side, which is not efficient and does not provide as much strength. Also, since the sides of the traditional square neck joint do not bear any tension, they do not contact the body and do not contribute to the resonance.
Some guitar designs solve this problem by making a neck run the entire length of the guitar; however, this design is more difficult to manufacture and not as aesthetically pleasing.
A need exists for a bolt-on guitar design that does not require a heel and that provides a strong and resonant connection between the neck and the body.